Quantum wave mixing on a single superconducting qubit produces a hierarchy of coherent side peaks associated with elastic multiphoton scattering pathways. In a cascaded source--probe geometry these pathways become sensitive to the photon statistics of the radiation emitted by the source qubit. We develop an analytical theory of this effect starting from the cascaded master equation in the weak-driving regime. In the coherent-filtering limit γs≫γpr, the standard coherent--coherent wave-mixing hierarchy is recovered. In the opposite limit γpr≫γs, side peaks associated with multiphoton absorption from the antibunched source field are parametrically suppressed. Numerical solutions confirm the analytical scaling laws. The resulting sideband hierarchy provides a frequency-domain fingerprint of antibunched itinerant microwave light.
@article{arxiv.2605.25828,
title = {Sideband fingerprints of antibunched light in cascaded quantum wave mixing},
author = {R. D. Ivanovskikh and W. V. Pogosov and A. A. Elistratov and A. Yu. Dmitriev and T. R. Sabirov and A. V. Vasenin and S. A. Gunin and O. V. Astafiev},
journal= {arXiv preprint arXiv:2605.25828},
year = {2026}
}